From d14e7683ecf06aa4365ee96adf74494114341dbe Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 29 Nov 2016 11:18:39 -0500 Subject: [PATCH] ext4: be more strict when verifying flags set via SETFLAGS ioctls Currently we just silently ignore flags that we don't understand (or that cannot be manipulated) through EXT4_IOC_SETFLAGS and EXT4_IOC_FSSETXATTR ioctls. This makes it problematic for the unused flags to be used in future (some app may be inadvertedly setting them and we won't notice until the flag gets used). Also this is inconsistent with other filesystems like XFS or BTRFS which return EOPNOTSUPP when they see a flag they cannot set. ext4 has the additional problem that there are flags which are returned by EXT4_IOC_GETFLAGS ioctl but which cannot be modified via EXT4_IOC_SETFLAGS. So we have to be careful to ignore value of these flags and not fail the ioctl when they are set (as e.g. chattr(1) passes flags returned from EXT4_IOC_GETFLAGS to EXT4_IOC_SETFLAGS without any masking and thus we'd break this utility). Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o --- fs/ext4/ext4.h | 1 + fs/ext4/ioctl.c | 28 +++++++++++++++++++++++----- 2 files changed, 24 insertions(+), 5 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 6e8b8e3fa4b7..f9958f661789 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -399,6 +399,7 @@ struct flex_groups { #define EXT4_FL_USER_VISIBLE 0x304BDFFF /* User visible flags */ #define EXT4_FL_USER_MODIFIABLE 0x204BC0FF /* User modifiable flags */ +/* Flags we can manipulate with through EXT4_IOC_FSSETXATTR */ #define EXT4_FL_XFLAG_VISIBLE (EXT4_SYNC_FL | \ EXT4_IMMUTABLE_FL | \ EXT4_APPEND_FL | \ diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index 834a1c10b2c2..2faeb3cdbbb3 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -415,6 +415,10 @@ static inline __u32 ext4_iflags_to_xflags(unsigned long iflags) return xflags; } +#define EXT4_SUPPORTED_FS_XFLAGS (FS_XFLAG_SYNC | FS_XFLAG_IMMUTABLE | \ + FS_XFLAG_APPEND | FS_XFLAG_NODUMP | \ + FS_XFLAG_NOATIME | FS_XFLAG_PROJINHERIT) + /* Transfer xflags flags to internal */ static inline unsigned long ext4_xflags_to_iflags(__u32 xflags) { @@ -459,12 +463,22 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) if (get_user(flags, (int __user *) arg)) return -EFAULT; + if (flags & ~EXT4_FL_USER_VISIBLE) + return -EOPNOTSUPP; + /* + * chattr(1) grabs flags via GETFLAGS, modifies the result and + * passes that to SETFLAGS. So we cannot easily make SETFLAGS + * more restrictive than just silently masking off visible but + * not settable flags as we always did. + */ + flags &= EXT4_FL_USER_MODIFIABLE; + if (ext4_mask_flags(inode->i_mode, flags) != flags) + return -EOPNOTSUPP; + err = mnt_want_write_file(filp); if (err) return err; - flags = ext4_mask_flags(inode->i_mode, flags); - inode_lock(inode); err = ext4_ioctl_setflags(inode, flags); inode_unlock(inode); @@ -871,13 +885,17 @@ resizefs_out: if (!inode_owner_or_capable(inode)) return -EACCES; + if (fa.fsx_xflags & ~EXT4_SUPPORTED_FS_XFLAGS) + return -EOPNOTSUPP; + + flags = ext4_xflags_to_iflags(fa.fsx_xflags); + if (ext4_mask_flags(inode->i_mode, flags) != flags) + return -EOPNOTSUPP; + err = mnt_want_write_file(filp); if (err) return err; - flags = ext4_xflags_to_iflags(fa.fsx_xflags); - flags = ext4_mask_flags(inode->i_mode, flags); - inode_lock(inode); flags = (ei->i_flags & ~EXT4_FL_XFLAG_VISIBLE) | (flags & EXT4_FL_XFLAG_VISIBLE); -- 2.20.1